A major achievement during the grant period has been the discovery of glyoxylic acid (GA) as highly potent histochemical reagent for biogenic monomamines, and the development of a fluorescence histocehemical method based on this reagent. This work will proceed along two lines: 1. The studies on the reaction mechanisms between GA and catechol-and indolamines will be continued and an analysis of the kinetics of the GA -catecholamine reactions will be made. 2. The GA method has proved extremely useful for detailed neuroanatomical studies of central catecholamine neurons. During the preceeding year we have initiated an extensive study of the organization of the ascending catecholamine systems in the brain. These studies will be continued, and we will focus above all on the catecholamine systems projecting to the neocortex, septum and hypothalamus. In addition to this work on the GA method we will continue our exploratory work on the neurotoxic properties of various hydroxylated indolamines, and study their usefulness as tools for experimental and neuroanatomical studies of central indolamine neurons. Our work on an identified intraneuronal indolamine in the rat brain stem is continued. We have recently obtained a gas chromatograph-mass spectrometer system which will allow us to attack this problem in a more rational way.